JP5559609B2 - Pivot bearing device - Google Patents

Description

  The present invention relates to a pivot bearing device having excellent accuracy for holding a shaft.

  For example, high bearing accuracy is required for a pivot bearing device used for a bearing portion of a swing arm that scans a magnetic head of an HDD (hard disk drive). This accuracy is particularly required in an HDD magnetic disk inspection apparatus that requires high-speed operation of the swing arm and high positioning accuracy. As a pivot bearing device that meets such requirements, a structure in which three ball bearings are arranged in the axial direction has been proposed (see, for example, Patent Document 1).

  In the pivot bearing device described in Patent Document 1, the accuracy of holding the shaft is increased by adopting a structure in which three ball bearings are arranged in the axial direction. The pivot bearing device described in Patent Document 1 has a structure in which the preload of the ball bearings positioned at the ends of three ball bearings arranged in the axial direction is double that of other ball bearings. In order to enable this preload state, the paragraph “0016” of Patent Document 1 states that the ball bearing to which the double preload is applied has a contact angle different from that of the other two ball bearings. Is described.

JP 2008-185190 A

  In the technique described in Patent Document 1, one of the three ball bearings needs to be a ball bearing having a different specification. For this reason, manufacture becomes complicated and component cost becomes high. Further, a ball bearing to which another preload is applied is likely to be worn out due to a strong load, which is disadvantageous in terms of reliability and life when considered as a whole pivot bearing device. Further, since the ball bearing having a high preload has a high torque, it is disadvantageous when a pivot bearing device having a low torque is obtained.

  Therefore, an object of the present invention is to provide a pivot bearing device that is easy to manufacture, has low component costs, has high reliability and a long life, and has low torque characteristics.

According to the first aspect of the present invention, a cylindrical outer member, a shaft member held inside the outer member, the shaft member held in a rotatable state with respect to the outer member, and axially A first ball bearing, a second ball bearing and a third ball bearing which are arranged in order, and only the outer ring of the second ball bearing is not fixed to the outer member, and the cylindrical shape A gap is formed between the inner side of the outer member and the outer ring of the second ball bearing, and the outer ring of the first and third ball bearings is connected to the cylindrical outer member via an adhesive layer. The pivot bearing device is characterized in that it is fixed inside and the gap is formed by the thickness of the adhesive layer . According to the first aspect of the present invention, the displacement of the position of the shaft center of the three ball bearings arranged in the axial direction is absorbed, and the fluctuation of the torque received when the shaft member is rotated can be suppressed. Note that the term “fixed” refers to a state in which it is fixed with an adhesive or the like and integrated so as not to move.

According to the first aspect of the present invention, the shift in the position of the shaft center of the three ball bearings arranged in the axial direction is absorbed, and fluctuations in torque received when the shaft member is rotated can be suppressed. The same specification can be used for all ball bearings. For this reason, manufacture is easy and can reduce a component cost. Further, since the specifications of the ball bearings are the same, a state where the load is concentrated on a specific ball bearing can be avoided, and high reliability and a long life can be obtained. Further, since three ball bearings are used, a pivot bearing device having a low torque characteristic by increasing the resonance frequency can be obtained. In addition, according to the first aspect of the present invention, a variation in the axial center of the second ball bearing is allowed, and a structure that absorbs a shift in the axial center position of the three ball bearings arranged in the axial direction is obtained. . In addition, according to the first aspect of the present invention, since no special processing for forming the gap is required, the manufacturing cost does not increase.

It is sectional drawing of the pivot bearing apparatus of embodiment. It is sectional drawing of the pivot bearing apparatus of embodiment. It is a conceptual diagram of the system which measures the fluctuation | variation of the torque received when rotating a shaft. It is a graph which shows the result of having measured the change of the torque received when rotating a shaft.

(Configuration 1)
FIG. 1 is a cross-sectional view of a pivot bearing device according to an embodiment. FIG. 1 shows a cross-sectional structure of the pivot bearing device 100 cut in the axial direction. The pivot bearing device 100 includes a shaft 101 that serves as a rotating shaft member and a cylindrical sleeve 102 that serves as an outer housing. The shaft 101 and the sleeve 102 are coupled by a first ball bearing 103, a second ball bearing 108, and a third ball bearing 113, and the shaft 101 can be rotated relative to the sleeve 102. Yes.

  Each ball bearing has the same specifications. The first ball bearing 103 includes an outer ring 103a, a ball 103b that functions as a steel ball that is an example of a rolling element, and an inner ring 103c. As the ball 103b rotates, the outer ring 103a rotates relative to the inner ring 103c. Similarly, the second ball bearing 108 includes an outer ring 108a, a ball 108b, and an inner ring 108c. Similarly, the third ball bearing 113 includes an outer ring 113a, a ball 113b, and an inner ring 113c.

  A through hole 101a is formed at the center of the shaft 101, and a female screw structure (not shown) is formed inside the through hole 101a. The male screw structure of another shaft member (not shown) is engaged with this female screw structure, whereby the shaft 101 is connected to the other rotating shaft.

  Near one end of the shaft 101, an annular flange (outer flange) 105 is integrally provided. The inner ring 103 c of the first ball bearing 103 is in contact with the flange portion 105. In addition, the outer ring 103 a of the first ball bearing 103 is in contact with an annular protrusion (inner flange) 102 a that is integrally provided inside the sleeve 102. The outer periphery of the outer ring 103 a of the first ball bearing 103 is bonded to the sleeve 102 by the adhesive layer 107, and the inner ring 103 c is bonded to the outer periphery of the shaft 101 by the adhesive layer 104.

  The preload applied to the first ball bearing 103 is applied between the flange portion 105 and the protruding portion 102a. That is, a force is applied in the order of the flange portion 105 → the inner ring 103c → the ball 103b → the outer ring 103a → the protruding portion 102a, and a preload is applied to the first ball bearing 103.

  The outer ring 108 a of the second ball bearing 108 is in contact with the protruding portion 102 a integrated with the sleeve 102 and the annular spacer 110. Here, the outer ring 108 a is not bonded (fixed) to the sleeve 102, the protruding portion 102 a, and the spacer 110. A gap 102b exists between the outer ring 108a and the sleeve 102. In this example, the inner diameter of the inner peripheral surface of the portion where the second ball bearing 108 of the sleeve 102 is located has a larger diameter structure than that of the other portion. That is, the inner peripheral surface of the sleeve 102 at a portion facing the outer ring 108a is configured such that the inner diameter is enlarged so that a gap 102b is formed between the outer ring 108a and the sleeve 102. In FIG. 1, the gap 102b is shown exaggerated for easy visual recognition.

  The outer periphery of the spacer 110 is in contact with the sleeve 102, and the upper and lower surfaces are in contact with the outer ring 108 a of the second ball bearing 108 and the outer ring 113 a of the third ball bearing 113. The spacer 110 is also in contact with other members, but is not fixed by adhesion or the like. The inner ring 108 c of the second ball bearing 108 is bonded to the shaft 101 with an adhesive layer 106. The inner ring 108c is not in contact with other members in the axial direction.

  The preload applied to the second ball bearing 108 is applied in the order of inner ring 108c → ball 108b → outer ring 108a → protruding portion 102a.

  The outer ring 113 a of the third ball bearing 113 is in contact with the spacer 110 and is further bonded to the sleeve 102 with an adhesive layer 112. Therefore, only the outer ring 108a of the second ball bearing 108 is not bonded. The inner ring 113 c of the third ball bearing 113 is bonded to the shaft 101 by the adhesive layer 111. The preload applied to the third ball bearing 113 is applied as follows: inner ring 113c → ball 113b → outer ring 113a → spacer 110 → outer ring 108a of the second ball bearing.

(Configuration 2)
FIG. 2 is a cross-sectional view of the pivot bearing device of the embodiment. FIG. 2 shows a cross section in which a pivot bearing device 200 having a structure different from that of the pivot bearing device 100 of FIG. 1 is cut in the axial direction. In the pivot bearing device 200, the shaft 101 and the sleeve 102 are coupled by the first ball bearing 103, the second ball bearing 108, and the third ball bearing 113, and the shaft 101 can rotate relative to the sleeve 102. It is a simple structure.

  In the following, a description will be given of the difference between the pivot bearing device 200 shown in FIG. The pivot bearing device 200 is different from the pivot bearing device 100 of FIG. 1 in that it includes a spacer 120 inserted in contact with the outer periphery of the shaft 101. The spacer 120 is in contact with the inner ring 108c of the second ball bearing 108 and the inner ring 113c of the third ball bearing 113, and transmits a preload between the inner ring 108c and the inner ring 113c. The spacer 120 is in contact with other members but is not fixed by adhesion or the like.

  Also in the pivot bearing device 200 shown in FIG. 2, there is a slight gap (not shown) between the outer ring 108 a and the sleeve 102. Here, in the pivot bearing device 200, unlike the structure of FIG. 1, the inner peripheral surface of the portion where the second ball bearing 108 of the sleeve 102 is located is not configured to have an increased inner diameter. These gaps have dimensions corresponding to the thickness of the adhesive layer 112 (about 0.5 μm to 50 μm). That is, as will be described later, the outer ring 113 a of the third ball bearing 113 is bonded to the sleeve 102 by the adhesive layer 112. On the other hand, the outer ring 108 a of the second ball bearing 108 is not bonded to the sleeve 102. Therefore, a gap corresponding to the thickness of the adhesive layer 112 is formed between the outer ring 108 a and the inner periphery of the sleeve 102.

  The preload in the pivot bearing device 200 will be described. First, the state in which preload is applied to the first ball bearing 103 and the second ball bearing 108 is the same as that of the pivot bearing device 100. Unlike the case of FIG. 1, the preload applied to the third ball bearing 113 is applied in the order of outer ring 113a → ball 113b → inner ring 113c → spacer 120 → inner ring 108c of the second ball bearing. The preload to the third ball bearing 113 is applied after the inner ring 108c is bonded to the shaft 101. Therefore, the preload applied to the third ball bearing 113 in the pivot bearing device 200 is received by the inner ring 108 c of the second ball bearing 108 and does not affect the preload already applied to the second ball bearing 108.

  As described above, the pivot bearing device 100 (or the pivot bearing device 200) shown in FIG. 1 (or FIG. 2) includes a sleeve 102 that is a cylindrical outer member and a shaft member that is held inside the sleeve 102. A certain shaft 101 and a first ball bearing 103, a second ball bearing 108 and a third ball bearing 113 which are held in a state where the shaft 101 can rotate with respect to the sleeve 102 and are arranged in order in the axial direction. And. The outer ring 108 a of the second ball bearing 108 is not bonded to the sleeve 102, and a slight gap is provided between the outer ring 108 a and the sleeve 102.

  Further, it further includes a projecting portion 102a that is integrally provided inside the sleeve 102 and is a contact member that is sandwiched between the outer ring 103a of the first ball bearing 103 and the outer ring 108a of the second ball bearing 108. ing. Further, a flange portion 105 provided integrally with the shaft 101 and contacting the inner ring 103c of the first ball bearing 103 on the side opposite to the second ball bearing 108 side of the inner ring 103c of the first ball bearing 103 is further provided. I have.

(Characteristic)
Hereinafter, the result of measuring the bearing accuracy of the pivot bearing device shown in FIG. 1 will be described. Here, two types of samples (A) and (B) were prepared. The sample of (A) is the pivot bearing device 100 shown in FIG. 1 which is an embodiment of the present invention. The sample (B) has a structure in which the outer ring of the second ball bearing 108 is further bonded to the sleeve 102 in the pivot bearing device 100.

(Measurement system)
First, the measurement system will be described. FIG. 3 is a conceptual diagram showing an outline of a system that performs measurement. In FIG. 3, a measurement system 400 is shown.

  In the measurement system 400, the sleeve 102 of the pivot bearing device 100 of FIG. 1 is attached to the rotary holder 401 via the holding sleeve 402. The rotation holder 401 is rotated by a drive motor 403. An extension shaft 404 is attached to the shaft 101 of the pivot bearing device 100, and a rotary arm 405 is attached to the extension shaft 404. A contact piece 406 is attached near the end of the rotating arm 405, and the detection part 407 of the load cell 408 is in contact with the contact piece 406.

  When the drive motor 403 rotates, the rotation holder 401 rotates, and accordingly, the sleeve 102 which is the outer casing of the pivot bearing device 100 tries to rotate relative to the shaft 101. At this time, since the contact piece 406 is in contact with the detection unit 407 of the load cell 408, the shaft 101 cannot rotate, and the torque received by the shaft 101 from the pivot bearing device 100 is measured by the load cell 408.

(Measurement result)
FIG. 4 is a graph showing the measurement results, where the horizontal axis is the measurement time corresponding to the relative rotation angle of the shaft 101 with respect to the sleeve 102 of the pivot bearing device 100, and the vertical axis is the torque that the shaft 101 receives from the sleeve 102. Is the value of FIG. 4A shows measurement data of sample A in which the second ball bearing 108 is not bonded to the sleeve 102. FIG. 4B shows measurement data of sample B in which the second ball bearing 108 is bonded to the sleeve 102.

  As is clear from FIG. 4, in the sample B in which three ball bearings are bonded to the sleeve 102, a periodic variation in torque with respect to the rotation angle is observed. On the other hand, in the sample A in which the second ball bearing (center ball bearing) 108 is not bonded to the sleeve 102, the torque variation with respect to the rotation angle is hardly seen. From this measurement result, it is concluded that a structure that does not adhere is superior in terms of suppressing torque fluctuation with respect to rotation, as compared with a structure in which the central ball bearing is adhered to the sleeve 102 that is the outer casing.

  Hereinafter, the cause of such a result will be considered. First, the radial positioning accuracy with respect to the shafts (rotating shafts) of the three ball bearings has a slight non-uniformity that is less than the measurement accuracy. In other words, the shaft centers of the three ball bearings do not completely coincide with each other, but are slightly shifted from each other (of course, they may coincide with each other by chance).

  Here, in the present embodiment, the central second ball bearing is not bonded to the sleeve 102, and a slight gap is provided between the outer ring and the sleeve 102. For this reason, it is considered that the relative positional relationship between the inner ring and the outer ring of the center ball bearing can be displaced to such an extent that the fluctuation of the center of each ball bearing is absorbed. This slight displacement absorbs the above-described deviation in the relative rotation of the shaft 101, and it is considered that the torque fluctuation hardly appears as shown in FIG.

  On the other hand, when the central ball bearing is bonded to the sleeve 102, the relative positional relationship between the inner ring and the outer ring of the central ball bearing is fixed, so there is no room for the deviation of the axial centers of the three ball bearings to be absorbed. Due to this deviation, it is considered that the fluctuation of the torque during the relative rotation of the shaft 101 appears as shown in FIG.

(Application examples)
The present invention can be generally used for a pivot bearing device, but is suitable for use in a pivot bearing device that holds a shaft with high accuracy. Examples of devices that require such a pivot bearing device include an inspection device for a magnetic recording medium used in an HDD and an axial pivot bearing device that supports a swing arm of a magnetic head in an HDD capable of high-density recording. . In these apparatuses, it is important to control the movement of the magnetic head quickly and quickly to a predetermined position. At this time, the holding accuracy of the pivot bearing device of the swing arm affects the data writing accuracy and reading accuracy. Specifically, when the accuracy of writing and reading data and the operation speed are increased, the bearing accuracy of the swing arm is required to be high accordingly. In this respect, the pivot bearing device using the present invention is suitable for use in these devices. Of course, it goes without saying that the pivot bearing device using the present invention can be used for other applications requiring high bearing accuracy.

  The present invention can be used for a pivot bearing device.

  DESCRIPTION OF SYMBOLS 100 ... Pivot bearing apparatus, 200 ... Pivot bearing apparatus, 101 ... Shaft (rotary shaft), 102 ... Sleeve (outer housing | casing), 102a ... Projection part, 103 ... 1st ball bearing, 104 ... Adhesive layer, 105 ... Flange 106, adhesive layer, 107 ... adhesive layer, 108 ... second ball bearing, 110 ... spacer, 111 ... adhesive layer, 112 ... adhesive layer, 113 ... third ball bearing, 120 ... spacer.

Claims (1)

A cylindrical outer member;
A shaft member held inside the outer member;
The shaft member is held in a rotatable state with respect to the outer member, and includes a first ball bearing, a second ball bearing, and a third ball bearing arranged in order in the axial direction,
Only the outer ring of the second ball bearing is not fixed to the outer member ,
A gap is formed between the inside of the cylindrical outer member and the outer ring of the second ball bearing,
The outer rings of the first and third ball bearings are fixed to the inside of the cylindrical outer member via an adhesive layer, and the gap is formed by the thickness of the adhesive layer. Pivot bearing device characterized.

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